51 21 140 Removing And Installing/Replacing Complete Lock Cylinder In Left Or Right Front Door: Replacement

Remove catches (1) and detach cover (2) from lock cylinder (3).

Installation: 

Catches (1) of cover (2) must not be damaged.

Paddle (4) of lock cylinder (3) must not be damaged.

Fig 1: Removing Catches & Detach Cover From Lock Cylinder

Courtesy of BMW OF NORTH AMERICA, INC.